This phone in particular will lag somewhat, but if it's terrible, you should consider trying a hard reset (Menu -> Settings -> SD card & phone storage -> Factory data reset **This will remove everything on your phone that isn't stored on the SD card or SIM card**).
I did that a few days ago, prior to rooting and installing a custom rom, and it helped tremendously. The phone will always be slightly laggy because of the TouchWiz UI, as mentioned above, but like I said, it shouldn't be really bad. I've seen completely stock Behold 2's that don't appear to be too laggy.
If you have patience, try rooting and installing a custom ROM from BH_MAN on these forums. You will not be disappointed. Performace increase is astonishing, especially since resident forum members are better at making phones work than our very own phone manufacturers.